1. Field of the Invention
The present invention relates to a getter which is able to maintain the vacuum by adsorbing the residual gases in a vacuum, in particular, a non-evaporating getter which is able to maintain the performance quality thereof over a long period of time even in the atmosphere tending to degrade the performance quality thereof, and a display unit equipped with such a non-evaporating getter.
2. Related Background Art
In general, the substance which can adsorb physically and chemically the residual gases in a vacuum is referred to as a getter. A material used as a getter is preferably a material that has a large speed of absorbing the residual gases in a vacuum and can maintain such a large adsorbing speed over a long period of time, for the purpose of maintaining the vacuum in which the getter is arranged over a long period of time as possible.
Conventionally, as such materials for getters, the elemental metals of Ba, Li, Al, Zr, Ti, Hf, Nb, Ta, Th, Mo, and V, and the alloys thereof have been known. Those getters, in which these elemental metals and alloys thereof are heated and evaporated in a vacuum to expose the neat metallic surfaces to which the residual gaseous components in the vacuum are adsorbed chemically, are referred to as evaporating getters. On the other hand, those getters, in which these metals and alloys thereof are heated in a vacuum to make the oxide layers to diffuse inward so that the metallic surfaces show up on the outermost surfaces at every time of heating to which surface the residual gases in the vacuum are adsorbed, are referred to as non-evaporating getters.
A non-evaporating getter is formed of an elemental metal substance containing Zr or Ti as the main component or an alloy containing these metals. Usually, in an actual usage, a film of these metals or alloys is formed on a substrate made of a stainless steel, nichrome, or the like, and the film is heated together with the substrate by means of energization heating or the like to make the gettering ability to be operative.
When a thin film of such an elemental metal as Zr or Ti is formed on a substrate made of a stainless steel, nichrome, or the like, according to a generally known method of vacuum evaporation or the like, however, extremely stable oxides are formed on the surface of the formed film at the instant of being exposed to the atmospheric air, and hence it is necessary to heat at the high temperatures 800 to 900xc2x0 C. in a vacuum for the purpose of forming active surface (Japan. J. Appl. Phys. Suppl. 2, Pt. 1, 49, 1974). Furthermore, the reactions between the thin films of these elemental metals subjected to the activation operation and the residual gases in a vacuum usually take place at 200xc2x0 C. or above, so that the thin films do not essentially show the gettering abilities around room temperature.
Consequently, a variety of improvements have hitherto been made in order to form a getter which is able to react with the residual gases in a vacuum at low temperatures so as to acquire a satisfactory gettering ability.
In the first instance, however, from the view point of cost, these improved getters unpreferably require labors in fabrication. In addition, there has been a drawback that the desired gettering characteristics cannot necessarily be maintained for a long period of time, depending on the environmental conditions under which it is used, since such a getter as is capable of exhibiting a satisfactory gettering ability at temperatures as low a""s room temperature is inevitably reactive, that is, fast in deterioration.
An object of the present invention is to provide a non-evaporating getter which can maintain the adsorbability for the residual gases, and in addition, can secure satisfactory characteristics particularly even when it experiences a high-temperature and low-vacuum condition in the process of the display unit fabrication.
Another object of the present invention is to provide a non-evaporating getter having the above described performance by means of a dry and convenient method.
Yet another object of the present invention is to provide a display unit which incorporates a non-evaporating getter having the above described performance and being excellent in display performance.
A non-evaporating getter of the present invention is characterized in that it comprises a substrate having no function as a getter and a polycrystalline film arranged on the substrate which film contains Ti as the main component and has a host of voids in the interior thereof.
In addition, the fabrication method of a non-evaporating getter of the present invention is characterized in that a polycrystalline film containing Ti as the main component is formed on the concavo-convex surface of the substrate which substrate has concavities and convexities on the surface thereof and does not have a function as a getter.
In addition, the display unit of the present invention which is equipped in its envelope with electron sources and phosphors each arranged to be opposing to one electron source is characterized in that the above described non-evaporating getter is arranged in the envelope.